A possible physiological role of milk epidermal growth factor in neonatal eyelid opening

The eyelid opening of newborn mice occurs normally on day 13.9 +/- 1.8 after birth. When newborn mice were injected with anti-epidermal growth factor (EGF) antibody every other day starting on day 1 after birth, the eyelid opening was delayed by approximately 3 days. The effect of anti-EGF became less prominent as the treatment was started at later times: when it was given from day 7, no delay in eyelid opening was observed. On the other hand, eyelid opening was enhanced by approximately 3 days by EGF injection given on day 3 for every other day. This effect of EGF was antagonized by simultaneous administration of the anti-EGF antibody. EGF was present at a concentration of 6.6 ng/ml in the plasma of 1-wk-old pups nursed by their mother, but it was not detectable (less than 0.1 ng/ml) in the plasma of 3-wk-old weaned pups. EGF concentration in the submandibular glands, however, was 17 times greater in 3- than in 1-wk-old pups, i.e., 4.66 and 0.28 ng/mg of wet tissue, respectively. These results suggest that milk EGF may play a physiological role in eyelid opening during the neonatal period.